Process for manufacturing multilayered foam articles

ABSTRACT

A process for preparing a multilayered foam article such as an automotive seat is disclosed. A mold is arranged so that the bottom surface of the mold is flat or inclined up to 40 degrees to the horizontal plane. The first liquid foam formulation designed to produce a soft foam is poured into the mold from a mixing head outlet strip-wise across the seating zone of the mold along the line parallel to but near the external wall of the seating zone of the mold. Then, the second liquid foam formulation designed to produce a hard foam is poured into the mold from the same or different mixing head outlet strip-wise across the seating zone of the mold along the line parallel to but nearer to the external wall of the mold than the line of pouring of the first liquid foam formulation. The second liquid foam formulation is then allowed to spread on top of the first liquid foam formulation, the mold is closed and the foames are allowed to rise and cure in the mold. The process produces an article having excellent layered-foam seating area.

The present invention relates to the preparation of multilayeredpolyurethane foam articles by the pouring of different foam formulationsinto a mold.

Multilayered or multihardness polyurethane foams are defined as layersof flexible foams of different hardness (load bearing) and/or densitywhich have a common flat boundary. These foams are usually used to makeseat cushions or squabs which have high SAG factors (that is, the ratioof hardness at high deflection to hardness at low deflection) andsuperior comfort, especially regarding H-point retention (seatoccupant's vertical position).

Various methods are known for the preparation of multilayeredpolyurethane foams. However the known methods suffer many disadvantagessuch as, for example, low productivity, thus high production costs; longfoam formulations pouring times; commingling of the foam formulationsresulting in a deformation of foam layers' boundaries, thus inferiorseating comfort for seat occupants.

One method for the preparation of multilayered polyurethane foam seatingis described in U.S. Pat. No. 4,190,697. This patent describes a processwhich involves pouring into a mold the first foam formulation which is ahard foam formulation, allowing it to rise for up to 45 seconds, andthen pouring the second foam formulation which is a soft foamformulation on top of the first foam formulation. The second foamformulation (soft foam) goes through the first foam formulation (hardfoam) and spreads as a liquid underneath the first foam formulationwhich has already risen to at least 10 to 80 percent of its potential.This process is based on the principle that the rising foam has lowerspecific density than the fresh liquid foam formulation. This process isnot practical for large industrial productions since it requires a longpouring time and, consequently is not widely used.

Another method for the preparation of multilayered polyurethane foamseating is described in European Patent No. 0'251'659. This patentdescribes a process which involves pouring sequentially two or more foamformulations, designed to produce two or more foams of differinghardness, onto a given point in the bottom of a seat mold and thereafterallowing the foam formulations to rise and cure. The seat mold isinclined to the horizontal plane and pouring point is located at, ornear, the top of the inclined bottom surface of the mold. It is afeature of this process that the formulations are poured sequentiallywithout any waiting time between, therefore in general little or nofoaming of any of the formulations takes place on a time scale on whichpouring occurs. Although, according to the patent, it would be expectedthat under such conditions, the formulations would mix, this does not,however, occur and, after curing, a foam seat comprising a discretelayer of the various foams is produced. The discrete foam layers arefound to be bonded to one another. In this process various foamformulations, which may, for example, be hard and soft foamformulations, originate from the same outlet on the mixing headproducing the formulations. The natural flow of each foam formulationdown the inclined surface of the bottom of the mold is relied on to fillthe mold evenly. This leads to a problem when such a process is appliedto large molds, for example, those used for the manufacture of rearseats for automobiles. In such cases, it is not only difficult to obtainuniform coverage of the bottom surface of the mold, but it is necessarythat the formulations have relatively long cream times to ensure thatcoverage is completed while the formulation(s) are still in anessentially liquid state. Another disadvantage of this process is thatthe time lag between pouring of two different foam formulations must bekept very short to avoid intermingling of the foam formulations in thelower part of the mold which would result in the deformation of thelayers' boundaries.

Another method for the preparation of multilayered polyurethane foamseating is described in European Patent No. 0'279'324. This processinvolves pouring a foam formulation designed to produce a soft foam ontoa given point in the bottom of a seat mold and allowing it to cream up,and then pouring a second foam formulation designed to produce a harderfoam next to the first foam formulation at the time when the first foamformulation has reached a suitable density and viscosity so that thefirst foam formulations is lifted up and enveloped by the second foamformulation. The fact that the first foam formulation must be partiallyexpanded before the second foam formulation is poured into the moldgives the same disadvantages as the process described in U.S. Pat. No.4,190,697, that is, it is not practical for large industrial productionssince it requires long pouring times.

Still another method for the preparation of multilayered polyurethanefoam seating is described in European Patent No. 0'393'827. This patentdescribes a process which involves pouring two different foamformulations strip-wise into the inclined mold from two differentoutlets which are arranged in a line. The two outlets poursimultaneously different foam formulations while they move across andabove the mold. The two outlets are attached to a single robot arm andthe distance between them is less than the width of the mold. Althoughthe speed of the robot arm is not indicated in this patent, it isobvious that the time interval between pouring the two different foamformulations is quite short. It has been found that with short timeintervals between pouring of the two different foam formulations whenthe outputs of the foam formulations are increased, or when there is aneed to pour the foam formulations very close to the upper side-wall ofthe mold, problems of turbulence may occur due to the velocity of thetwo liquids when they hit the bottom surface of the mold. The effect isthat the second foam formulation which is poured onto the first foamformulation tends to push the first foam formulation downwards withintermingling of the two foams in the lower part of the mold. Theresulting layered-foam article has inferior comfort properties.Moreover, due to the fact that the two pouring outlets are attached to asingle robot arm and the foam formulations are poured simultaneouslyinto the mold, the respective waiting and pouring times cannot beadjusted for different mold designs.

It is evident that there is still a need for a process for preparingmultilayered foam articles which process is versatile with respect todifferent mold designs, giving good foam vibration properties and stillallowing for fast pouring of liquid foam formulations into a mold to beviable for use on fast moving industrial foam production lines.

It has now been discovered that the problems found in the aforementionedpatents can be overcome by certain modifications to the procedure bywhich the foam formulations are poured into the mold.

In particular, it has surprisingly been discovered that pouring thesecond liquid foam formulation designed to produce a hard foam onto thebottom mold surface inclined to the horizontal plane at a place whichhas not been wetted by the first poured liquid foam formulation designedto produce a soft foam, contrary to the teachings of European Patent No.0'251'659, produces a laminar flowing of the second liquid foamformulation on top of the first foam formulation.

It has also been surprisingly discovered that the strip-wise pouring ofliquid foam formulations according to the present invention allows notonly for a longer time interval between pouring of the two foamformulations than with the fixed (one place) pouring, but also producesthe flow of the second liquid foam formulation on top of the firstliquid foam formulation. Thus the two-step pouring regiment can beaccommodated on a dual-hardness foaming equipment with only one mixinghead. In addition, the two-step strip-wise pouring allows pouring ofliquid foam formulations on mold surfaces which are horizontal, and evenslightly inclined in the opposite direction of the flow of the liquidfoam formulations and still obtain formation of foam layers.

It has also been discovered the two step strip-wise pouring of theliquid foam formulations according to the present invention, whetherfrom a single outlet or from two outlets, permits longer pouring timefor one liquid foam formulation than the other liquid foam formulation.This allows control of relative thickness of both foam layers.

It has also been discovered that the mixing head(s) outlet(s) which arenormally kept vertical in relation to the horizontal plane can be tiltedto change the direction of the foam reactants flows during pouringoperation. Surprisingly, the tilting of the mixing head(s) outlet(s)results in increased thickness of the second foam (soft) relative to thefirst poured foam without changes in liquid foam formulations outputs orin pouring times.

It has also been discovered that layered foam articles produced by theprocess of the present invention have good vibration properties.

Accordingly, the present invention concerns a process for preparing amultilayered foam article in a mold arranged so that the bottom surfaceof the mold is flat or inclined up to 40 degrees, preferably between 0.1and 15 degrees, to the horizontal plane by foaming and curing a firstliquid foam formulation and a second liquid foam formulation in the zoneof the mold corresponding to a seating area of the multilayered article,characterized in that the process comprises the following steps:

(a) pouring the first liquid foam formulation into the mold strip-wiseacross a zone of the mold from a mixing heat outlet; and

(b) pouring the second liquid foam formulation into the mold strip-wiseacross said zone of the mold, from the same or a different mixing headoutlet, parallel to the pouring of the first liquid foam formulation butspaced therefrom such that the second liquid foam formulation contactsthe mold where the mold has not been wetted by the first liquid foamformulation and allowing the second liquid foam formulation to spread ontop of the first liquid foam formulation.

Where the article has a seating zone, said steps are preferably carriedout by:

(a) pouring, across the seating zone of the mold, strip-wise from amixing head outlet, the first liquid foam formulation designed toproduce a soft foam into the mold along the line parallel and near tothe external wall of the seating zone of the mold; and

(b) pouring, across the seating zone of the mold, strip-wise from thesame or different mixing heat outlet, the second foam formulationdesigned to produce a hard foam into the mold parallel to but nearer tothe external wall of the mold than the line of pouring of the firstliquid foam formulation and allowing the second liquid foam formulationto spread on top of the first liquid foam formulation.

The present invention solves problems of the aforementioned prior artand provides a process for preparing multilayered foam articles which isversatile with respect to different mold designs, gives a layered foamarticle with a well defined common flat boundary between the foam layersand good foam vibration properties, and still allows for fast pouring ofliquid foam formulations into a mold to be viable for use on fast movingindustrial foam production lines.

The process of the present invention can be operated either in a moldhaving the bottom surface flat to the horizontal plane or in the moldhaving the bottom surface inclined from the back to the front of themold at an angle of between 0.1 and 40 degrees to the horizontal plane.This inclination of the mold bottom surface may be achieved by actuallytilting the mold or by employing a mold which has been manufactured withan inclined bottom surface. In fact, for most conventional automobileseat molds, the incline in the mold running from the back to the frontof the seat is sufficient for the purposes of this invention.Preferably, the angle of incline is 4 to 20 degrees, most preferably 5to 12 degrees.

The process of the present invention is particularly applicable toautomobile seat molds, for making seats and back rests such as thosewhich comprise a central seating area arranged between two supportingside rolls.

Low or high pressure, up to 250 bars, single-mixing head or multiplemixing heads mounted on a 5-axes robot arm, or on a 2-axes manipulatorare suitably used in the process of the present invention. A singlemixing head capable of pouring two different foam formulationssequentially, or multiple mixing heads with independent manipulators,can be used in the process of the present invention. Mixing heads having2 or more, up to 8, preferably 2 to 4, additives and polyol blendsstreams and 1 or 2 isocyanate streams, are suitable for use in theprocess of the present invention. The speed of mixing heads can bevaried during the pouring of different foam formulations or the mixingheads can even be stopped for a short interval of time at some pointabove the mold to increase pouring time in a particular zone in themold.

If multiple mixing heads are used, the distance between outlets andtheir respective positions can be varied depending on the moldingconditions.

In one embodiment of the present invention, the liquid foam formulationdesigned to produce foams of different hardness (load bearing) arepoured simultaneously from at least two mixing heads outlets strip-wiseinto the seating zone of the mold along different lines while the mixingheads move above and across the seating zone of the mold.

In another embodiment of the present invention, the first liquid foamformulation designed to produce a soft foam is poured strip-wise intothe mold along the line parallel and near to the external wall of theseating zone of the mold and after an interval of from 0.05 to 1 0seconds, the second liquid foam formulation designed to produce a hardfoam is poured strip-wise into the mold along the line parallel to butnearer to the external wall of the mold than the line of pouring of thefirst liquid foam formulation.

Still in another embodiment of the present invention, the first liquidfoam formulation designed to produce a soft foam is poured from a mixinghead outlet strip-wise along a line parallel and near to the externalwall of the seating zone of the mold and then the second liquid foamformulation designed to produce a hard foam is poured from the same ordifferent mixing head outlet strip-wise along the line parallel to butnearer the external wall of the mold than the line of pouring of thefirst liquid foam formulation in the opposite direction to the directionof pouring of the first liquid foam formulation.

Still in another embodiment of the present invention, the liquid foamformulations designed to produce foams of different hardness are pouredsequentially from at least two mixing heads outlets strip-wise into theseating zone of the mold along different lines across the seating zoneof the mold.

Yet in another embodiment of the present invention, the mold movesrelative to the mixing head(s) outlet(s) during the pouring of theliquid foam formulations.

Normally, the mixing heads are kept vertical relative to the horizontalplane while the liquid foam formulations are being poured into the mold.However, the mixing heads outlets can be tilted (inclined) relative tothe vertical plane while the liquid foam formulations are being pouredinto the mold.

The speed of movement of the mixing heads outlets above the mold or thespeed of movement of the mold relative to the mixing heads can varybetween 0.1 and 150, preferably between 0.5 and 30 m/minutes

The foam formulations to be used in the present invention are suitablypolyurethane foam formulations, although it is envisaged that theprocess of the present invention could be applicable to other polymerfoam systems such as, for example, polyurea.

Polyurethane foams are well known in the art and comprise the productobtained by mixing a polyfunctional isocyanate with a polyfunctionalactive hydrogen containing compound (for example, a polyether polyol) inthe presence of a blowing agent and allowing them to react undercontrolled conditions of temperature, pressure and catalysts. In theprocess of the present invention, such mixtures are generated in themixing head and then poured into the mold through the outlet before themixture has started to rise, that is, while the foam formulation isstill in an essentially liquid state.

The process of the present invention can be used with any type offlexible polyurethane foam formulations including “hot-cure” and“cold-cure” formulations.

The polyurethane foam formulations useful in the process of the presentinvention are those producing flexible foam, most preferably flexible HR(high resilience) foams. In such a case, two streams are fed to themixing head; one comprising a formulated polyol, that is, some or all ofpolyols, polymer polyols, blowing agent, catalysts, siliconesurfactants, blowing agents and other additives; the other comprisingthe polyisocyanate.

Any known polyether polyol, blends of polyether polyols, copolymerpolyols (such as, for example, SAN, PHD, PIPA), blends of copolymerpolyol, blends of polyols with copolymer polyols can be used in theprocess of the present invention.

Any known organic polyisocyanate can be used in the process of thepresent invention. These polyisocyanates include those containing atleast about 2 isocyanate groups per molecule, preferably, thosecontaining an average of from 2.0 to 3.0 isocyanate groups per molecule.The preferred polyisocyanates used in the practice of this invention arearomatic polyisocyanates and include the toluene diisocyanates,especially mixtures of the 2,4- and 2,6-isomers such as those containing65 percent of the 2,4-isomer and 35 percent of the 2,6-isomer (TDI65/35), and those containing 80 percent of the 2,4-isomer and 20 percentof the 2,6-isomer (TDI 80/20); and polyisocyanate mixtures comprising2,4′- or 4,4′-methylene diphenylisocyanate (MDI);hexamethylenediisocyanate (HMDI); polymeric MDI; andisocyanate-terminated prepolymers thereof. Mixtures of two or morepolyisocyanates can also be used in the process of the presentinvention. The polyisocyanates can be used at all known ratios.

Any known catalyst used in the preparation of polyurethanes such as, forexample, amines and metal salts, alone or in combination, can be used inthe process of the present invention. The catalysts are generally usedin a quantity of between 0.002 and 10 percent by weight, based on thetotal quantity of polyol.

Water is used as the main blowing agent in the process of the presentinvention at the level of from 0.5 to 10, preferably from 2 to 6 partsper hundred parts of polyol. Auxiliary blowing agents such as carboxylicacids or organic or inorganic compounds that liberate gas by reactionwith polyisocyanate or under effect of heat, and inert gases such ascarbon dioxide, can also be used in the process of the presentinvention.

Any crosslinking agent known in the preparation of polyurethanes suchas, for example, glycerol, diethanolamine (DEOA) and triethanolamine(TEOA) can be used in the process of the present invention. Thecrosslinking agent is used in a quantity known to a person skilled inthe polyurethane art.

Any type of known foam modifiers, such as those described in U.S. Pat.No. 4,686,240 can be used in the process of the present invention. Thefoam modifiers are used in a quantity known to a person skilled in thepolyurethane art.

Other known additives such as, for example, silicone surfactants,pigments, fillers, and plasticizers can also be used in the process ofthe present invention. The additives are used in a quantity known to aperson skilled in the polyurethane art.

Temperature of the liquid foam formulations (polyol and polyisocyanatecomponents) can vary between 10 and 80, preferably between 15 and 35,degrees Centigrade.

The flexible polyurethane foam formulations used in the process of thepresent invention are preferably chosen such that they differ inhardness (load bearing) from each other. It is further preferred thatsuch formulations differ in hardness by virtue of their content of oneor more of the following: (a) polyols, (b) polyisocyanates with afunctionality greater than two, that is, with more than 2 isocyanategroups per molecule, (c) active hydrogen-containing compound which maybe a chain extender or crosslinker, and (d) blowing agent. In thecontext of the present invention, the soft foam has lower hardness (loadbearing) than the hard foam.

During pouring operation, molds are kept at a temperature rangingbetween 20 and 80, preferably between 35 and 75, degrees Centigrade.Molding in a fabric shaped inside the mold, with or without insulatingfilms or foam interliners, such as described in U.S. Pat. No. 4,755,411,is also possible with the process of the present invention.

The molded polyurethane foam articles are cured at a temperature ofbetween room temperature and 250 degrees Centigrade conveniently for aperiod of time between 2 and 20 minutes, before demolding.

The following designations, symbols, terms and abbreviations are used inthe Examples below:

CP-6001 is a glycerol initiated polyol (having a Molecular Weight of6,000 and an EO content of 75 percent) sold by The Dow Chemical Companyunder the trademark VORANOL CP 6001.

CP-1421 is a cell opener sold by The Dow Chemical Company under thetrademark VORANOL CP 1421.

Dabco 33LV is a 33 percent solution of triethylene diamine indipropylene glycol sold by Air Products and Chemicals Inc. under thetrademark DABCO 33LV.

Dabco 8154 is an amine catalyst sold by Air Products and Chemical Inc.under the trademark DABCO 8154.

Niax A-1 is 70 percent bis(2-dimethylaminoethyl)ether solution in DPGold by OSi Specialties Inc.

Niax A-4 is an amine catalyst sold by OSi Specialties Inc.

DIPA is diisopropanolamine (containing 90 percent diisopropanolamine and10 percent water).

TIPA is triisopropanolamine (containing 90 percent triisopropanolamineand 10 percent water).

DC-5043 is a surfactant sold by Air Products and Chemicals Inc. underthe trademark Dabco 5043.

B-4113 is a silicone surfactant sold by Th. Goldschmidt under thetrademark Tegostab B-4113.

B-4690 is a silicone surfactant sold by Th. Goldschmidt under thetrademark Tegostab B-4690.

NE-106 is an MDI prepolymer sold by The Dow Chemical Company under thetrademark SPECFLEX NE 106.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention defined above will now be illustrated with reference tothe following Examples which make reference to the accompanying drawingsin which:

FIG. 1 is a side view of a front seat mold showing pouring of two liquidfoam formulations from vertically positioned mixing heads outlets.

FIG. 2 is a top plan view of the front seat mold shown in FIG. 1.

FIG. 3 is a side view of another front seat mold showing pouring of twoliquid foam formulations from mixing heads outlets tilted in relation tothe vertical plane.

FIGS. 4A and 4B are cross-sections of molded foam articles made in themold shown in FIGS. 1 and 2.

FIG. 5 is a top plan view of another front seat mold.

FIG. 6 is a cross-section of a molded foam article according to thepresent invention made in the mold shown in FIGS. 3 and 5.

FIG. 7 is a cross-section of a molded foam article made according to aprior art process.

FIG. 8 is a top plan view of the mold shown in FIG. 5 showing two mixingheads aligned at an angle of 25 degrees in relation to the line parallelto the external wall the seating zone of the mold.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1

An automotive seat mold (1) shown in FIG. 5 comprising a central seatingzone defined by rectangular A, A′, R and R′, two side-rolls zones (a,b), and a thigh support zone (c) was employed. The mold was made ofaluminum and arranged so that the bottom surface was inclined at anangle beta of 4 degrees to the horizontal plane. The inside surfaces ofthe mold kept at 55 degrees Centigrade were sprayed with the LK 260 moldrelease agent sold by Th. Goldschmidt. The two mixing heads (3,3′) withoutlets (4,4′) were connected to respectively a Krauss Maffei RIMSTAR40/10 and a Krauss Maffei KK 10-5/5 machine. The two mixing headsoutlets were mounted on a 5-axes ASEA 90 robot arm with the mixing headoutlets separated by a distance of 12 cm. With this arrangement themixing heads outlets were used to dispense respectively soft and hardliquid foam formulations. The two mixing heads outlets were in verticalposition at the distance of 40 mm above the bottom surface of the moldduring the pouring operation. The actual composition of the foamformulations are given in Table I.

The operating conditions were as follows: The polyol stream temperaturewas 30 degrees Centigrade. The polyisocyanate stream temperature was 22degrees Centigrade. The pressure for both polyol and polyisocyanatestreams was 170 bars. Total output for foam formulation A was 214 g/sand for foam formulation B was 172 g/s. Total weight of foam formulationA poured into the mold was 1355 g and total weight of foam formulation Bpoured into the mold was 250 g.

The pouring procedure was as follows: The two vertical mixing heads(3,3′) with outlets (4,4′) were arranged to form an angle γ of 25degrees with the external wall (5) of the seating zone of the mold. Thisarrangement of the mixing heads outlets is schematically illustrated inFIG. 8 where the two mixing heads are identified with numerals 13 and12, respectively. The soft foam formulation A was poured from the mixinghead outlet (12) and the hard foam formulation B was poured from themixing head outlet (13). After filling the side-rolls zones (a, b) andthe thigh support zone (c), which is separated from the seating zone bya dividing wall (6), with the foam formulation A, the two foamformulations A and B were poured simultaneously and strip-wise from thetwo mixing heads outlets into the seating zone of the mold. The firstfoam formulation A was poured along the line P-P′ while the second foamformulation B was poured along the line R-R′ which was closer to theexternal wall of the seating zone of the mold. The robot arm speed wasabout 14 m/minute during the strip-wise pouring of the foamformulations.

After pouring of both foam formulations was completed, the mold wasclosed with the lid (2), and the foams were allowed to rise and cure.FIG. 6 shows the cross-section taken along the line E-E′ shown in FIG. 5of the resulting demolded seat cushion. The resulting demolded foam seatcushion has an excellent flat layer of a soft foam (8) on top of a hardfoam (9). The hard foam layer was 40 mm thick and the soft foam layerwas 30 mm thick measured at 14 cm from the external side of the seatingzone.

Surprisingly, with this pouring technique the second foam formulation B(hard foam) although was poured on a place into the mold which has notbeen wetted by the first foam formulation A (soft foam), flows on top ofthe first foam formulation and forms a regular and flat layer.

TABLE I Formulation A (soft) B (hard) C (soft) D (hard) CP-6001 parts 9898 100 100 CP-1421 parts 2 2 none none Water parts 3.275 3.275 3.4 3.4DIPA parts 1.25 1.25 none none TIPA parts none none 1.0 1.0 B-4690 partsnone none 1.1 1.1 DC-5043 parts 0.6 0.6 none none B-4113 parts 0.4 0.4none none Dabco 33LV parts 0.5 0.5 0.4 0.4 Niax A-1 parts 0.075 0.075none none Niax A-4 parts none none 0.15 0.15 Dabco 8154 parts none none0.4 0.4 NE-106 parts 52.5 68.5 49 71.8 NE-106 Index 80 105 75 110

EXAMPLE 2

This example illustrates another embodiment of the present invention.The mold, the mixing head(s) outlet(s), the processing conditions andfoam formulations used were as described in Example 1 except that the 2foam formulations were poured sequentially. As shown in FIG. 8, thepouring procedure was as follows: The first foam formulation A (softfoam) was poured strip-wise from the mixing head outlet (12) along theline P-P′. Then, the robot arm was moved to bring the mixing headsoutlets back to their original position. After waiting for 0.5 seconds,the second foam formulation B (hard foam) was poured strip-wise from themixing head outlet (13) along the line R-R′. Since the speed of therobot arm is the same as in Example 1 and the width of the seating zoneis 350 mm, it had been calculated that over 3 seconds had been spentbetween pouring of both foam formulations.

The resulting demolded seat cushion has a flat layer of a soft foam ontop of the hard foam as uniform as the one in Example 1.

Comparative Example 1

The mold, the mixing heads, the processing conditions and foamformulations used were as described in Example 1 except that the twofoam formulations were poured according to the teaching of EuropeanPatent No. 0'393'827, that is, the two foam formulations were pouredsimultaneously from the two mixing heads outlets (arranged in a line)strip-wise along the line R-R′ of the mold shown in FIG. 5. The two foamformulations intermingled near the dividing wall A-A′. The hard foamlayer was only 35 mm thick in comparison with the 40 mm thickness of thehard foam layer obtained by the process of the present invention. It isevident that the prior art process of European Patent No. 0'393'827produces an inferior layered foam seat cushion due to the interminglingof the two foam formulations and lower thickness of the hard foam layerwhich results in a lower support or sag factor. The resulting demoldedseat cushion is illustrated in FIG. 7.

EXAMPLE 3

The mold, the mixing heads outlets, the processing conditions and foamformulations used were as described in Example 1 except that the twomixing heads dispensing the two foam formulations were aligned so thatthey formed an angle γ of 90 degrees with the external wall of theseating zone of the mold. Such arrangement of the two mixing headsoutlets resulted in pouring foam formulation B (hard foam) almost 12 cmabove foam formulation A (soft foam). The resulting demolded seatcushion has a flat layer of a soft foam on top of the hard foam.

EXAMPLE 4

An automotive seat mold shown in FIGS. 1 and 2 was employed. The moldcomprised a central seating zone defined by rectangular R, R′, P and P′,two side-roll zones (a, b) and a thigh support zone (c) as illustratedin FIG. 2. The mold was made of aluminum and arranged so that the bottomsurface was inclined at an β of 3 degrees to the horizontal plane. Theinside surfaces of the mold were kept at 60 degrees Centigrade sprayedwith the LK 260 mold release agent sold by Th. Goldschmidt. The twomixing heads (3, 3′) with outlets (4, 4′) were connected to respectivelya Krauss Maffei RIMSTAR 40/10 and a Krauss Maffei KK 10-5/5 machine. Thetwo mixing heads outlets were mounted on a 5-axes ASEA 90 robot arm withthe mixing heads outlets separated by a distance of 12 cm. The twomixing heads outlets were in a vertical position to the horizontal planewhile dispensing liquid foam formulation C (soft foam) and liquid foamformulation D (hard foam), respectively. The actual composition of thefoam formulations are given in Table I.

The operating conditions were as follows: The polyol stream temperaturewas 30 degrees Centigrade. The polyisocyanate stream temperature was 22degrees Centigrade. The pressure for both polyol and polyisocyanatestream was 160 bars. Total output for foam formulation C was 214 g/s andfor foam formulation D was 150 g/s.

The soft foam formulation C was poured from the mixing head outlet (4)and the hard foam formulation D was poured from the mixing head outlet(4′). After filling the side-roll zones and the thigh support zone (c)with the foam formulation C, the 2 foam formulations C and D were pouredsimultaneously and strip-wise from the 2 mixing heads outlets into theseating zone of the mold. The first foam formulation C was poured alongthe line P-P′ while the second foam formulation D was poured along theline R-R′ which was closer to the external wall of the seating zone ofthe mold. The robot arm speed was about 14 m/minute during thestrip-wise pouring of the foam formulations.

After pouring of both foam formulations was completed, the lid of themold was closed, and the foams were allowed to rise and cure. Theresulting demolded seat cushion had a weight of 1,440 grams and a flatlayer of a soft foam (8) on top of a hard foam (9) as illustrated inFIG. 4A. The hard foam layer was 45 mm thick and the soft foam layer was35 mm thick measured at 14 cm from the external side of the seatingzone.

EXAMPLE 5

The mold, the mixing heads, the processing conditions, and foamformulations used were as described in Example 4 except that the twomixing heads outlets dispensing the two foam formulations were tilted atan angle α to the vertical plane of 8 degrees in the direction of theslope of the bottom surface of the mold as illustrated in FIG. 3.

The resulting demolded seat cushion had a weight of 1,432 grams and anexcellent flat layer of a soft foam on top of the hard foam. The hardfoam layer was 50 mm thick and the soft foam layer was 30 mm thickmeasured at 14 cm from the external side of the seating zone.

EXAMPLE 6

The mold, the mixing head(s) outlet(s), the processing conditions, andthe foam formulations used were as described in Example 4 except thatthe two mixing head(s) outlets dispensing the two foam formulations weretilted at an angle a to the vertical plane of 14 degrees in thedirection of the slope of the bottom surface of the mold as illustratedin FIG. 3.

The resulting demolded seat cushion had a weight of 1,430 grams and anexcellent flat layer of a soft foam on top of the hard foam. The hardfoam layer was 52 mm thick and the soft foam layer was 28 mm thickmeasured at 14 cm from the external side of the seating zone.

EXAMPLE 7

The mold, the mixing heads outlets, the processing conditions and foamformulations used were as described in Example 4 except that the twomixing heads outlets dispensing the two foam formulations were tilted atan angle α to the vertical plane of 25 degrees in the direction of theslope of the bottom surface of the mold as illustrated in FIG. 3.

The resulting demolded seat cushion had a weight of 1,405 grams and anexcellent flat layer of a soft foam on top of the hard foam asillustrated in FIG. 4B. The hard foam layer was 50 mm thick and the softfoam layer was 30 mm thick measured at 14 cm from the external side ofthe seating zone.

It should be understood that the present invention may be varied in manyways. Such variations are not to be regarded as a departure from thespirit and scope of the invention, and all such modifications as wouldbe obvious to a person skilled in the art are included within the scopeof the following claims.

What is claimed is:
 1. A process for preparing a multilayered foam article in a mold arranged so that the bottom surface of the mold is flat or inclined up to 40 degrees to the horizontal plane by foaming and curing a first liquid foam formulation designed to produce a softer foam and a second liquid foam formulation designed to produce a harder foam, characterized in that the process comprises the following steps: (a) pouring the first liquid foam formulation into the mold strip-wise across a zone of the mold from a mixing head outlet; and (b) pouring the second liquid foam formulation into the mold strip-wise across said zone of the mold, from the same or a different mixing head outlet parallel to the pouring of the first liquid foam formulation but spaced therefrom such that the second liquid foam formulation contacts the mold where the mold has not been wetted by the first liquid foam formulation and allowing the second liquid foam formulation to spread on top of the first liquid foam formulation; characterized in that the mixing head(s) outlet(s) are tilted relative to the vertical plane while the liquid foam formulations are being poured into the mold.
 2. The process according to claim 1, characterized in that the liquid foam formulations designed to produce foams of different hardness are poured simultaneously from at least two mixing heads' outlets strip-wise into said zone of the mold along different lines while the mixing heads move above and across said zone of the mold.
 3. The process according to claim 1, characterized in that the liquid foam formulations designed to produce foams of different hardness are poured sequentially from a single mixing head strip-wise into said zone of the mold along different lines across said zone of the mold.
 4. The process according to any one of claims 1 to 3, characterized in that the first liquid foam formulation designed to produce a soft foam is poured strip-wise into the mold and after an interval of from 0.05 to 10 seconds, the second liquid foam formulation designed to produce a hard foam is poured strip-wise into the mold.
 5. The process according to claim 4, characterized in that the first liquid foam formulation is poured strip-wise in a first direction and then the second liquid foam formulation is poured strip-wise in an opposite direction to the line of pouring of the first liquid foam formulation.
 6. The process according to claim 4, characterized in that the mold moves relative to the mixing head outlet or outlets during the pouring of the liquid foam formulations.
 7. The process according to any one of claims 1, 2 or 3, characterized in that the liquid foam formulations are flexible polyurethane foam formulations.
 8. The process according to claim 7, characterized in that an article comprising a layered foam seating area is produced.
 9. A process as claimed in claim 8, wherein the pouring of the first and second formulations is carried out along respective lines near an external wall of the mold.
 10. A process as claimed in claim 9, wherein said lines are parallel to said wall. 